I saw the Discovery Channel documentary on the Bismarck yesterday. It told about how bad the wheather was the day that all the Brittish ships moved in on the Bismarck, after it’s rudder got stuck. They started fireing on the Bismarck from 23 kilometres away, in very rough wheather. So that got me wondering, did the guns on those ships already have gyro’s to keep them level while the ship rocked on the waves?
From old footage I concluded that WWII tanks didn’t have them, so I always supposed that using a gyroscope for this purpose was a later invention.
If they didn’t have them on ships, how did they aim at a ship 23 KM away? And if they did use them on ships, how did they work, without computers? And in that case too: why didn’t they use them in tanks?
Actually, WW2 battleships did have “computers” – big analogue electro-mechanical devices that could only calculate targeting solutions. Would never fit in a tank of the age. Target information would be input from optical rangefinders atop the masts and/or from radar, plus from the ship’s own motion/speed/weather conditions instrumentation (some input directly, some manually). Then you would start by “bracketing” the theoretical target point with ranging fire, and your rangefinders would tell you if you were long or short, right or left. You STILL do this with today’s naval gunnery, only your instrumentation feeds the correcting info to the computer directly.
See here down this page where it says “FM Division” for a full explanation of WW2 Battleship fire-control.
American battleships did indeed have early analog compters in the latter stages of the war. All they did was compute where to point the guns taking into your velocity, the enemy’s velocity and your current postions. Everybody else had to make the same calculations using slide rules and guesswork. See this page for more details.
There was no gyro stabilisation, you just had to hope that the guns were fired when your ship was level.
A while ago I watched a documentary on HMS Belfast (still moored IIRC in the Thames.) a WWII British warship. It did have one of the analogue computers mentioned above and was involved in hunting one of the big German battleships although I can’t remember which one.
Actually some WWII tanks did have gyro stabilization. Shermans manufactured after 1942 were equipped with an elevation-only gyro. It performed poorly and because of its tendency to fail was frequently disconnected by crews.
I suppose that the computer included a gyroscope to measure the ships’ roll. The guns could then be fired by the computer when the ship was level AND the gun captains had signaled “Ready.”
So far you have only heard half the answer. The guns did not have gyro’s becuase they did not need them. It worked something like this:
As you can imagine, a 40,000 ton ships has a pretty long roll period. When the gunnery solution is found, it assumes a gun angle. For example, the firing solution assumes a 15 degree gun elevation. What the crew did, was simply wait untill the gun rolled to 15 degrees, then fired the gun. For the purist, this explaination is simplified and other systems existed, at least one of which which essentially used human gyro’s.
This would not work in a tank because the gun in jumping around too fast for a human to control. However, the main gun on these ships moved very slowly.
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the system was a little more complicated than I had thought. The gun angles were corrected for roll and pitch. Here is a quote from the site’s section on gun fire control systems from 1939 to 1950. The fire control computer included sections for target tracking and trajectory computations, fuze timing and;
“A Correction Section (calculating and applying corrections due to own ship angular actions, namely roll and pitch requiring trunion tilt and deck tilt corrections to the gun angles.)”
So the guns were gyro stabilized by the computer which corrected the computed gun angles to account for own ship motions of roll and pitch.
The fact that battleships of that time had a hit rate anywhere from 10 to 25 percent (25 being phenominally lucky) would probably tell you they did not have any kind of gun stabilizing mechanism other than large springs. Of course the size of the shell meant that even with a 10 percent accuracy rating, any hit would be devastating.
Gyroscopes have two properites, rigidity in space and precession. A top secret weapon of WW2 was anti-aircraft weapons that used precession to calculate an aircraft’s position in the future. The shooter(s) would follow the aircraft in their sights. The precession of the gyros would allow the guns to “lead” the target so that shell had a good chance to hit the target. There were two shooters, one followed the horizontal movement of the target, the other followed the vertical movements.
What did smaller ships with shorter roll period do?
Someone else said that Shermans had(unreliable) gyros but I have heard that IIRC the British Challenger tank used the gunner(standing) as a human gyro.
Here is a description of a destroyer’s operations in WW2, includes a looong chapter halfway down the page on how the main battery, AAs and the FC system worked for that type of combatant. If I understand it correctly, it could be set up so that when the gyros read an angle within the “window” calculated by the targeting computer, there would be a signal to fire. Also when fire-for-effect was called, the main battery could go to as fast as 20-shells-per-minute so it wasn’t as if every single shot had to be on-the-spot.
